Ion's are known for being unreliable
They are ? First I've heard of it. I've heard a few negative stories like with any marker, but the vast majority have been positive.
The advantages of an Ion are its a good solid marker, with plenty of upgrades. its downside is you will 'need' to buy a few upgrades. (By need I mean it is highly advisable, but you can live without them.) A q-lock, and an ASA for starters. A 14 inch barrel to replace the standard 12 inch if you want more range.
It is however designed as a starter tournament marker, (worth a lot more than its price tag mind you,) and yes the PM5 does beat it overall as the PM5 is/was a top end tourny marker, but there's nothing wrong with having an Ion when you are starting out. Just ignore the sneers of the people with the latest 07 model £1000 markers, as they are just compensating for their lack in other area's.....like people who buy Porsches and Ferrarri's
And what Spangly said about people knowing about Ion's.