It's been a while, but I finally completed my update of the Urusov Gambit coverage at http://www.ianchessgambits.com/urusov-gambit.html
I've managed to get the ChessBase dynamic diagrams working, which allow viewers to move the pieces. The new ChessBase game replayers is, I think, a significant improvement over the old one but I found that having multiple instances of the replayer on one web page caused glitches, so I have chosen to provide links to the annotated examples that are published using the One Click Publishing feature.
As for the assessment of the gambit, the accepted lines still seem to be holding up well, but of the declining lines, 4...Bb4+ does, as Michael Goeller suggested a while ago, appears to be the main problem at high levels, if Black aims for equality by striking out in the centre with a well-timed ...d5. However, in the Chesslive.de database, Black tends to follow up 4...Bb4+ poorly, and so the move is scoring only 41% for Black. The highest-scoring reply for Black is the more well-known 4...Nc6 transposing to the Two Knights Defence (where Black is scoring 49%). Black is scoring 44% after grabbing the bait with 4...Nxe4.
For White, if faced with a prepared opponent, there are some ideas for unbalancing the position after 4...Bb4+. There is 5.c3 dxc3 6.0-0 0-0 (6...cxb2 7.Bxb2 and as in many such lines, it is unclear if White has two pawns' worth of compensation, but White's initiative is extremely dangerous) 7.a3!? (7.bxc3 d5), which gives some compensation, though I'm not sure if it is objectively enough. More definitely sound but less in the gambit-style are 6.bxc3 d5 7.cxb4!?, and 6...Bc5 7.e5 d5 8.exf6 dxc4 9.Qxd8+.
I don't expect to be giving up the Urusov anytime soon, having had a lot of fun with it in practice, but in view of 4...Bb4+ as well as 4...Nc6, I don't expect it to catch on among grandmasters either.