Ok, request for a scholar/historian's view on Jizyah - here is an extract from such a person. The link gives the full text and also the references he uses (I've not included the footnotes in the extract, but the link gives all the footnote references).
PREACHING OF ISLAM
A History of the Propagation of the Muslim Faith
BY
Sir Thomas W. ARNOLD
Pg 54 to 57:
Enough has been said to show that the Christians in the early days of the Muhammadan conquest had little to complain of in the way of religious disabilities. It is true that adherence to their ancient faith rendered them obnoxious to the payment of jizyah or the capitation-tax, but this was too moderate to constitute a burden, seeing that it released them from the compulsory military service that was incumbent on their Muslim fellow-subjects. Conversion to Islam was certainly attended by a certain pecuniary advantage, but his former religion could have had very little hold on a convert who abandoned it merely to gain exemption from the jizyah ; in certain cases also, instead of the kharaj or land-tax, he was allowed to pay a tithe on the produce, but in other cases the kharilj was exacted even after conversion. But, instead of jizyah, the convert had now to pay the legal alms, zakat, annually levied on most kinds of movable and immovable property.
The rates of jizyah fixed by the early conquerors were not uniform, and the great Muslim doctors, Abu Hanifah and Malik, are not in agreement on some of the less important details the following facts taken from the Kitabu-1 Kharaj, drawn up by Abu Yusuf at the request of Harunu-r Rashid (a.d. 786-809) may be taken as generally representative of Muhammadan procedure under the Caliphate. The rich were to pay 48 dirhams a year, the middle classes 24, while from the poor, i.e. the field-labourers and artisans, only 12 dirhams were taken. This tax could be paid in kind if desired ; cattle, merchandise, household effects, even needles were to be accepted in lieu of specie, but not pigs, wine, or dead animals. The tax was to be levied only on able-bodied males, and not on women or children. The poor who were dependent for their livelihood on alms and the aged poor who were incapable of work were also specially excepted, as also the blind, the lame, the incurables and the insane, unless they happened to be men of wealth ; this same condition applied to priests and monks, who were- exempt if dependent on the alms of the rich, but had to pay if they were well-to-do and lived in comfort. The collectors of the jizyah were particularly instructed to show leniency, and refrain from all harsh treatment or the infliction of corporal punishment, in case of non-payment.
This tax was not imposed on the Christians, as some would have us think, as a penalty for their refusal to accept the Muslim faith, but was paid by them in common with the other dhimmis or non-Muslim subjects of the state whose religion precluded them from serving in the army, in return for the protection secured for them by the arms of the Musulmans. When the people of Hirah contributed the sum agreed upon, they expressly mentioned that they paid this jizyah on condition that " the Muslims and their leader protect us from those who would oppress us, whether they be Muslims or others." Again, in the treaty made by Khalid with some towns in the neighbourhood of Hirah, he writes, “If we protect you, then jizyah is due to us ; but if we do not, then it is not due." 5 How clearly this condition was recognised by the Muhammadans may be judged from the following incident in the reign of the Caliph 'Umar. The Emperor Heraclius had raised an enormous army with which to drive back the invading forces of the Muslims, who had in consequence to concentrate all their energies on the impending encounter. The Arab general, Abu 'Ubaydah, accordingly wrote to the governors of the conquered cities of Syria, ordering them to pay back all the jizyah that had been collected from the cities, and wrote to the people, saying, We give you back the money that we took from you, as we have received news that a strong force is advancing against us. The agreement between us was that we should protect you, and as this is not now in our power, we return you all that we took. But if we are victorious we shall consider ourselves bound to you by the old terms of our agreement." In accordance with this order, enormous sums were paid back out of the state treasury, and the Christians called down blessings on the heads of the Muslims, saying, " May God give you rule over us again and make you victorious over the Romans ; had it been they, they would not have given us back anything, but would have taken all that remained with us."
As stated above, the jizyah was levied on the able-bodied males, in lieu of the military service they would have been called upon to perform had they been Musalmans ; and it is very noticeable that when any Christian people served in the Muslim army, they were exempted from the payment of this tax. Such was the case with the tribe of Jarajimah, a Christian tribe in the neighbour- hood of Antioch, who made peace with the Muslims, promising to be their allies and fight on their side in battle, on condition that they should not be called upon to pay jizyah and should receive their proper share of the booty. When the Arab conquests were pushed to the north of Persia in a.h. 22, a similar agreement was made with a frontier tribe, which was exempted from the payment of jizyah in consideration of military service.
We find similar instances of the remission of jizyah in the case of Christians who served in the army or navy under the Turkish rule. For example, the inhabitants of Megaris, a community of Albanian Christians, were exempted from the payment of this tax on condition that they furnished a body of armed men to guard the passes over Mounts Cithseron and Geranea, which lead to the Isthmus of Corinth. Similarly, the Christian inhabitants of Hydra paid no direct taxes to the Sultan, but -[furnished instead a contingent of 250 able-bodied seamen to the Turkish fleet, who were supported out of the local treasury. The Mirdites, a tribe of Albanian Catholics who occupied the mountains to the north of Scutari, were exempt from taxation on condition of supplying an armed contingent in time of war. 2 In the same spirit, in consideration of the services they rendered to the state, the capitation tax was not imposed upon the Greek Christians who looked after the aqueducts that supplied Constantinople with drinking-water. On the other hand, when the Egyptian peasants, although Muslim in faith, were made exempt from military service, a tax was imposed upon them as on the Christians, in lieu thereof.