Aprillia Rss are highly strung bikes with very tight tolerances.
Cut short if you race it around reving the tits off it in every gear it will last you about a month, If you treat it nicely and use good quality 2 stroke oil etc, it will last ages.

A few friends of mine had them bikes when they first came out years ago and the people that looked after them had the bike for the a long time. (they tend to eat chain and sprockets though and the CDI unit needs replacing every few years).

http://www.maxmoto.co.uk/aprilia_rs125.shtml
That page has a fare bit of info on it, well worth the read.

Ps. I have a friend who might be selling an Immaculate RS125, It was imported from Italy a few years ago and its the top bollox one not the restricted one you get in the Uk.

TBH Soopahfly there all horrible buzzy things.
I had a Yamaha DT 50 for my first bike and I bloody hated it.

in that case, given my limited knowledge and the purpose of getting the bike... would a cbr125 be a more reliable option?

I only want something to practice on (whilst still moderately cool ) before i do the practical test, then ill get something bigger, but restricted

Dunno how old you are Wilbo so Ill make just spurt this crap out and you can decide how relevant it is

If youre going to do an A2 Restricted test and you have no plans on buying a bigger bike and restricting it then get yourself a 125 that youll be happy with.

If youre going to do a DAS test then dont spend more than a few hundred notes on your 125 because as soon as you pass youll want a bigger bike.

Your first years insurance will be a bit of a shocker (well I thought so). My CBR125RR cost just shy of £220 3rd Party F&T. A CBF500 (restricted) will cost me £410 FComp...and I am 30

I decided to do an A2 Restrcited test as I wasnt sure how bothered I would be about owning a bike. For me it was more about having something to do, a new challenge.
I bought a 6month old CBR125RR to use for practice, my plan was to sell it once I had passed my test...
...however I think I have no decided that I am going to keep it until I have 1yrs ncd; hopefully making a larger bike a little cheaper to own

My CBR is for what I use it for at the moment; mainly shooting into town. Itll do 75-80mph on a flat strech but thatll drop back to 70(or less) on a hill (like those on the M3 south bound around Winchester). As a result Im not using the bike on motorways, its just not up to it (imo)...but its fine on dualcarriage ways.