Love my VAIS SL2i-UP and never ran into any limitations.
If one listens to a small number of playlists and doesn't do much if any searching for songs or playlists and doesn't care much about the navigation and display (or hasn't used anything better) then I can see how there's lots more to love than hate. Since I hit most of the limitations below every time I listen, it erks me a bit. We hold the vehicle in high regard and have the expectation that lots of thought went into every feature and it's a let down when some of the features don't hold up to that reputation of good quality and good design. Luckily I didn't buy the vehicle for it's stereo system
The limitations offhand that I can think of:
- more of a lack of features than limitations, but the other units I've used allow you to do a fast skip ahead instead of moving forward one song or playlist at a time. As an example, if you have 99 playlists and you're currently at number 49 but want to get to 99 you need to push the friggin button 50 times. If you were at 1 and wanted to get to 99 iirc you can at least go backwards

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- same limit/lack of features for songs except worse since if you have a few hundred (or say 999) songs in a playlist and you want to get to 400 you could sit there for a while skipping forward or backwards and it puts unnecessary stress on the buttons to say the least. Other systems would allow you to either fast skip (hold down the button and it skips faster like 10 at a time instead of 1 at a time), or they allow you to skip to the first letter you're looking for.
- also the display doesn't show you more than x characters - it cuts off long text displays of band or song name.
- no way to see song and band and album at the same time. You can either see the song or the band or the album but not more than one of those at a time. And guess what you have to push to change that display - a button called disc rpt (iirc). intuitive right?
- no way to fast forward within a song - you can skip to the next or go back but can't fast forward.
- the display only shows you one song at a time. Other displays I've seen will show you ahead and behind (like 5 at a time with the one you're on highlighted) so you can see what you're looking for. This one shows just one at a time.
- this is preference not functional, but still - the look and feel of the dispaly is terrible (but admittedly usable). never seen a production system with such a piss poor display. I would have been embarrassed if I were associated with the product in any way shape or form - it is not fit for a top of the line vehicle like the LC or LX - not even for their bottom of the line.
- can't handle more than 99 playlists. Right off the bat I had well over a hundred
- can't handle more than 999 songs in a given playlist. personally I have well over that on numerous playlists.
- also with regard to the 99 and 999 limitations is that their instructions say (iirc) if you exceed their limits the behavior could be unexpected (iirc they use the kind of language that says to me "we have no idea how it will behave" and "all hell may brake loose").
I have other observations on the lack of functionality in the satellite navigation and bluetooth, but I'll leave that for another post where it would be on topic
I went a slightly different route on my 03 lx. I installed a USA spec interface behind the dash and a pro-clip iPhone holder on the dash. The setup charges the phone with the case on and plays through the factory stereo perfectly. You can use the steering wheel controls for track selection.
I use it everyday. You can even rotate phone and watch Netflix while the audio comes through the stereo (while stopped).
Can you elaborate on this solution? What is the "USA spec interface" you are referring to? Any writeups or products you can point us to? I'm curious to see more about it.
Thanks!