I like Holtz because he had clear motivations for what he did, and his character seemed consistent. Only a man of great will and cunning would've survived Angelus and Darla as long as he did, and no demon is going to turn such a man into a mindless lackey (at least not if he wants to keep Holtz a finely tuned weapon). He was both brilliant and understandable (and also charismatic no matter what time period he's in), and also well acted (his line of "I swore I'd show no mercy, and I won't" always gives me chills). As an added bonus, he doesn't turn into a rage-filled moron at the end like so many villains in so many shows do, he stays his willful, devious self up to the very end (and the only problem I have with his suicide is that there'd be blood everywhere, unlike a vampire attack, but the demonic energies of Qortoth coursing in him and twisting his mind, combined with his own phenomenal willpower and incredible hatred already present, does make me think he could really do it).
That said, let's take a moment to reflect on what an utter moron Sahjan is. A time traveler who can transport people through time, at least the future, and he could've made people rich who terminated Angel's existence before he was even born or before he was turned, and probably could've even tipped off Holtz while he was hunting him in the past. He could also help people win bets and stocks in the more modern world on the condition they hire the Order of Taraka or whatever to take out Angel before Connor is born. Heck, why not send Angel to Qortoth himself if he thought it was a good enough end for Connor? I swear the Senior Partners had to cast a feeblemind spell on him to neuter him as a threat for him not to do any of these things. Him, I don't care for at all. (Though his yelling at Lilah in front of Angel was good for a laugh to move the plot forward, if another example of how stupid he is.)
