I have had the promount 18 for about three months and think it's just brilliant, well worth the money.
i think i've been one of the lucky ones as no problems so far (don't want to speak too soon :

I'm amazed at the constant output of high heat, it's pretty much steam even at 300 ft

i did find it needed descaling after 1 1/2 months, all got totally blocked all of a sudden, but the descaler i got from woodbridge (hope i'm allowed to mention them

) was so strong it cured it straight away and nearly made me pass out as i couldn't get out of the van quick enough!
apart from that all ok, think i will get a water softener tho as water is very hard here.
cheers
steve