Sorry for the delay, been crazy at work today and ended up working through lunch when I intended to reply.
Are they reliable - I'd estimate that I've put over 35000 cartridges through mine over the last 2.5 years and never had an issue, someone previously said that cheaper cartridges were an issue but I've only ever shot Gamebore Velocity+, DTL Elite, EJC Hellfire, Black Gold game plus a few odds and sods and never had pierced primers. The ejectors are fantastic, shoot empties miles.
Are they worth the price tag - for me yes, I shoot it very well and there has been the odd thought of switching to a K which has been quickly dismissed as I'd only end up setting it up to shoot the same as the F3.
Is the back up good - they come with a ten-year warranty from new. Touch wood mine has been fine.
Any problems or niggles - just go careful with the barrel weights as they can come loose, just worth checking each time when you've finished shooting.
Do the barrels rust or discolour as some people suggest - I've not got any rust on mine, I generally give all the metalwork a wipe over with an oily rag most times I use it, every time if it's been raining.
Do they handle well - very well, the benefit of having the stock & barrel weights is that you can set it up to how you want it.
Do they hold their value - I don't think they hold their value as well as others but depends if you sell privately or use it as part exchange or straight sale to a gun shop.