Ion rocks....
I got an Ion and am very pleased with it. Yes it aint a dye or ego or whatever, but for the money it rocks!! Buy second hand if you can, as you should be able to buy a stock one or slightly upped one for around the £100 mark from the forum classifieds.
The Ion is infinitely upgradeable, so you can start cheap to match your budget, then buy ups as required to either increase practicality and/or efficiency, and if you so wish, to make it look flash.
As you posted, immediately get a Q-lock to ensure you secure your hopper on properly. I would also recomend a CP OOPs (On Off Purge System). Don't know where you are situated but LPS fitted both for me for about £50.
I would recomend a used Egg to keep up with your Ion (about £30 from forums). I got an Egg and other than minor minor niggles with the battery door (solved after battery mod, or use electricians tape), it keeps up with my Ion and hasn't let me down once.
Ultimately you will want to upgrade, however my two penneth worth is to just get the q-lock on your Ion to start with, then start attending pball days and then see what else you feel you need. Try not to get caught up in upgrade mania if you on a budget, which I think we all are in some form or the other.
Oh... 15bps as per the UK capped limit.. but a stock Ion is said to be able acheive 17bps uncapped. However if you got money tree you can buy top dollar upgrades for it (basically replace all the innards) and apparently it can do 30+ bps.... Not that you would ever have the chance to use it playing pball so waste of money possibly?
Hope this is useful.
Have fun with your Ion. It rips......