I've given my impressions numerous times before, but I think I have just about all the books she's written so far. This puts it all in one place, at least. Watch out for spoilers.
Since Teddypig commented on it, I'll start with the "With or Without" series. I gave "With Love" to S. as a gift. Now that's I've read some yaoi stories and learned about bishonen, it is easy to see Laine as looking classically bishonen in appearance. He's certainly meant to be a uke. Laine isn't virginal, but he's so cute. I just loved him and Devlin together. Dev was just determined to take care of Laine from the moment they met. I crack up every time about what Laine does to Caroline near the end of the story, to keep her out of the way.
As I've mentioned, Without Reservations is one of the very few, if not the only, "Gay for You" stories that has worked for me. Somewhere between Chay and Keaton being mates, and Chay having experimented in college, it clicked enough to justify it for me. I adored Keaton as a character. Again we have a gorgeous little bishonen of a man, but he's so fiery-tempered and stubborn. It wasn't too clear who was submissive, but it certainly wasn't Keaton in general. I like stories in which the protagonists are versatile, and Chay turned out to be pretty versatile. He was also so easygoing and just a nice person. I didn't see how Remi would be redeemed after how he acted in Without Reservations, but getting his screwed-up point of view helped somewhat. Poor Jake -- I think Keaton and Chay both say that, actually. But Jake was awesome in With Caution. I couldn't really see why they needed all those accessories when it was already just naturally so clear who had which role. I did like the retroactive continuity to explain why the Alpha in "With Love" was so interested that way in Laine. Remi going from obnoxious in Without Reservations to submissive in With Caution was a puzzling change for me, because he still didn't act submissive towards anyone but Jake, when they were making love. Considering where he was in the pack hierarchy, I would have expected him to act submissive towards the other werewolves. The plot other than the romance had some gaps in the logic, but her protagonists pull you into the story, and you just go along for the wacky ride.
The short stories about Rhys and Sterling just made me that much more anxious to read their story when it comes out. Without Fear is currently on hold, but J.L. is working on With Abandon, Matt's story. I saw an excerpt for it -- on Fiction with Friction? (http://www.fictionwithfriction.com) -- and am eager to read that one, too.
The Sci-Regency series: Took me a while to try it, as I thought the blurb for My Fair Captain was horrible, but as I've noted elsewhere, between Lisabea's (http://lisabea.blogspot.com) enthusiastic recommendations and Samhain's offer to read the first half free, I went for it and got totally hooked. It was hard to figure out that Sire, Cony, King-Consort and Raleigh were all the same person, but once I realized that, it all made much more sense. The plot other than the romance isn't too well developed, but I didn't really care. Like "With Love," the editing could have been better. Ms. Langley has a tendency to use "may" when she should use "might," just as one example, but somebody on the proofing side of things should have caught that. The romance plot swept me away right along with Nate and Aiden. It was a little jarring to have modern-day BDSM mixed with a Regency romance, but Nate was finely depicted as a dominant character, and Aiden was so innocent and eager to please.
The Englor Affair had a more sensible secondary plot, with a nice mix of romance and a little bit of intrigue. Simon and Payton were so good together, and I liked that Payton was so clever. Sometimes he outsmarted himself, but that just made it more fun.
"A Regelence Christmas" and "Happy Valentine's Day, Sir" (http://www.jllangley.com) were cute little short stories that go with the series. They definitely add to the ambiance of the Sci-Regency world and the characters.
The Ranch Series: I liked The Tin Star, and loved The Broken H. I just really enjoyed the interaction between Shane and Gray, and I liked Gray's other family members, too. Jamie and Ethan of The Tin Star were good characters, also.
"One Good Favor," in The Ties That Bind was cute, too. I liked the characters in that, and in "His Convenient Husband," even if the latter had an extremely typical romance plot. Holy crap, I just got an idea of who Dick D., Langley's co-author for "One Good Favor," might be. Having a horse who liked to destroy cell phones was a very cool touch.