I never looked at them and only had a quick look now:
Hi/Lo freebitco.in gameFirst of all the house edge is 5%. There is nothing wrong with that, but most sites have a 0.5 - 1% house edge (and SatoshiDice highest with 1.95%.) Since they do give away free money and lottery entries, again I don't think there is anything wrong with it. But a "real dice player" probably should play somewhere else.
Provably fairThey use a "nonce" but yet they change the serverseed after each roll. So I am not sure why they would use that nonce
With the "per roll" provably fair implementation, it's important that the site regenerates an unique client seed in the browser after getting the new serverseed hash after each bet. freebitco.in doesn't do this. This means IMO the provably fair implementation of them is "not really" provably fair.
Basically it allows them to serve a serverseed based on bet patterns (if you always go high, they would generate a low result.) The counter argument is that they shouldn't do this, because if they do this - you as a player can heavily cheat them too (bet 10x high, then a big low bet = easy profits.) Of course they could do it more subtle/smart. But besides that, the least they can do is make a result that isn't 8888 (jackpot), to scam jackpot entries completely unnoticeable.
I don't think they do this, but they should still fix this. Rollin had the same and fixed it:
https://bitcointalksearch.org/topic/--687571 You can see more details/fix there too.
Note, that you CAN still bet provably fair on their site. It just takes some time: 1) Click "provably fair" 2) write down "Hash" and "Nonce" 3) change the "Client seed" 4) make bet 5) verify bet (their link seems fine.) You will need to do this for EVERY bet.
LotteryLottery is not provably fair at all. So yeh, "house player" can always win everything. If they want to implement a provably fair lottery, they should look into how PevPot used to do it.
TL;DR: personally I would gamble on other sites with proper provably fair implementations (preferably with real nonce-implementation.)