Well, Ted, i have to admit to being guilty of sentiment - like classic car & bike enthusiasts, i still tend to hand on to the old iMP decks fondly in memory..
The 550 would have been a contender for me, at one time, but it's shockingly poor tolerence of media (as noted from plenty of feedback posted over the last year or so here and at iRiver) definately made it a downgrade from my buying point of view.
Pity really, as the 350 (early/mid builds) had all the hyper level of disc tolerence the 250 had - but by comparision, the poor 550 is a relative prima donna when it comes to what it'll accept in the way of user's own recorded media.
So, as 550 owners realise, the days of cheapo media are a piece of history as far as modern iMP decks use is concerned
As it goes, reflecting on the 250, the old tolerence was simple.. if the disc was correctly burnt within it's real media tolerence and the disc hadn't got physically deep damaged by mishandling, it'd read fine on the old decks - pick any modern deck and try putting the same deep-damaged disc in.. and listen to the poor motors working overtime :P
Vinnie :-
Sure, without sounding like a broken record, the only bit of the whole Ogg adoption argument i do agree with is the fact that a proper range of support should have been added.. or nothing.
So, for iMP/iFP use people have two choices .. take a chance and stick to a narrow Q range for encoding, or literally ABR encode to the known supported rate limits.
Clearly, ABR encoding is slower than slow.. VBR is better but still snails pace stuff (relatively speaking).
Since iRiver are clearly in no hurry to fix the limited support bit, it's sane that anyone with no time to waste.. had better stick to ABR encoding with the specific player support limits punched in...