Let me just start by saying my title probably covers the majority of people here, regardless of what you think of L4. L3 was a great product and blessed many for many years. Even today it continues to bless those who use it to study the scriptures.
For those who may be formulating their opinions of L4, or perhaps are already leaning on the negative side, I would like you to consider some of the following benefits of L4 that were not present in L3. Your opinion of L4 is yours to have. Mine is very favorable and I love trying to sell it on these forums. Perhaps the following points do not sway you, but they do me and perhaps will for others as well.
Sympathetic Highlighting - L3 had no equivalent to sympathetic highlighting. It makes it far easier to find things in the originals, apostolic fathers, and in comparing translations.
Savable Guides - I love not having to run the guide every time I start up, L3 could sometimes take a while. With the benefits of notes and future enhancements I'm not sure any of us truly understand the benefit this will have
Customizable Guides - I love being able to combine Exegetical elements with the passage guide. I can set on guide up to match the flow of my sermon prep, starting with a quick look at the textual variants (Apparatus section), then word by word, parallel resources occasionally visual structure, cross references, commentaries, etc.
Syncing - I have not needed to search for one disc. I can understand the indexing and downloading can take a while but I'm not all that organized. I spent more time waiting on the mail, digging up old discs, installing them (My L3 Gold took at least an hour to get from CD to HD) then I have on indexing. Plus all my notes come right along after having to re-install (had to because of the 1st beta)
Multi-monitor and layout - I love the way they allowed for multi monitor. I love the new layout. This will be a matter of taste. For me it is a huge plus
Word Study Word Rings - I find the L4 word rings far superior. There are many enhancements in the Word Study report that are easy to take for granted. Interlinears with Auto Sympathetic highlighting in the Word for Word, for example. You can add to this the preposition report which was absent from L3.
Documents - This too will be a matter of taste. I find the new "File" section far better for managing my documents. Rather then searching through drop down menus I just type "notes" or if I know the name of the note I can search by that.
Visual Filters-I'm getting far more use out of L4 visual filters then L3. I hated going in and messing with them in L3.
Searching Library - Almost forgot it because it goes without saying
Mobile support -Still developing, but the fact that it's implemented and possible is a huge bonus.
Reading Lists- I like them and I hope they continue to develop.
Command line - Another taste thing, but once you get used to it things become much faster. For instance to close everything ALT + D, ca enter does it for me because I made a layout with nothing and called it ca. To change layouts is all with the keyboard for me.
Biblical People/Places/Things - These have been very beneficial to me on many occasions.
Dynamic Collections - Big improvement in my Opinion.
Favorites Management - Another big improvement.
I'm out of time but I'm sure there is more I could post. All I ask is that you consider these benefits in formulating your opinion. I can't wait to see the improvements they bring over L3 as they implement the missing features!