Had a mille R (ohlins front and rear) after my first firestorm, very different, if you don't like them then you don't get them !, fantastic bikes, handle very well, not masses of top end but more than a firestorm, they rip through the revs much quicker too.
Thrash them and you'll get 90 odd miles to a tank, but if cruising on the motorway i could get 160 miles before the fuel light, comfy for touring too
I had the first model R with the gloss black paint and red, didn't like the later matt black ones, I still think the 2000 model was the best looking of the lot and they only made it for 1 year (so could be worth more in years to come). From new The ohlins forks dive too fast under braking, you can dial some of it out but not all, I had ohlins superbike internals put in mine, made a massive difference only cost £150 fitted back in 2001, also had the rear shock re sprung and valved for me at the same time, any bike fitted with the ohlins will need a revalve by now anyway so budget for it and use it to bargain.
Thumper, the nitride is on there to help lower friction as the fork slides through the seals, no need to have them fully coated.
Problems.. The fork seals are low friction and can leak fairly often, you don't need to change them, just strip them, clean them and reassemble with red rubber grease, or there's other seals that fit, iirc a model of R1 and a model of GSXR1000 seals fit but can't remember which models now.
Sprag clutches can go and aren't easy to fix, some go so bad they crack the crank case, the reason mostly is if they stall they need a second or so to settle before you restart them or the motor kind of locks and the sprag fails, they're a high compression twin, if you stall it don't just hit the starter, wait a sec then start, also make sure your battery is fully charged as a low battery can have the same effect.
On 04 onwards bikes the oil tank can split near the filter. also on the later models some suspension linkages have failed and killed people

a few have failed world wide, there were lawsuits and stuff going on, Aprilia never did a recall and never admitted anything, a big was the linkage breaking or wasn't it broken during the accident thing. Never had any problems with mine or my Tuono's, but you can fairly cheaply get beefier linkage plates if your worried.
Working out the clocks will give you plenty of bog reading time, make sure you get the handbook with the bike.
Interesting fact; if you fit a one tooth smaller front sprocket they have a higher top speed, Aprilia fitted a bigger front to lower the revs to help get them through the drive by noise tests, they used to supply the smaller sprocket with the bike, in a packet under the seat hump, also it won't effect the speedo as the it picks up off the rear disc bolts (so don't fit stainless or titanium ones or you'll have no speedo)