In reply to Andy S:
I've used 2 in the past - Optimus Nova and Primus Omni-Fuel.
Optimus Nova
Pluses - the nova did me a season in the alps comfortably burning petrol and paraffin - no clogging issues (though I did take care to clean / service it often). The pump unit is metal, so much more durable that MSR plastic pumps (I know several people who have broken theirs). Weight was higher as a result (but not much overall as the burner unit its self was smaller and lighter. More compact that MSR as well. Problems I did have: the breather tube was never very securely attached - I ended up gluing it in repeatedly as it was falling out all the time. I never found it to be as fast on the boil as MSRs, but it was a little more fuel efficient. Simmer control was poor as well - most of the adjustment didn't seem to do anything.
Omni-Fuel.
This has been my favourite so far! Seems very fuel efficient, easy to dismantle / service. The fact that you can use it with Gas Canisters as well as liquid fuel adds more flexibility.
Combined with a Primus heat exchanger pot its massively fuel efficient.
No mechanical issues so far, though I've only had it 18 months and not had the chance to test it long term with petrol / paraffin like the nova.
Side by side with mates MSRs it seems better made, with a more robust pump.
It comes with different jets for different fuels - so you can optimise for best performance, or just fit the nozzle for the most restrictive fuel and live with the less efficient burning on other fuels.
Neither seems nearly as prone to the "MSR Fireball" on startup (though this is probably as much about the user as the stove.......).
Anyway - hope that's of help!
Cheers,
Stu