Nothing Ventured, Nothing Gained?

So in the beginning of dating someone new, where does one draw the line on going out just one more time to see if anything develops, and just saying, there's no chemistry or attraction there so lets end it? So this new woman, the hiker, here-to-fore known as Ms. Long Legs, has a ton of great qualities...great personality, funny, sweet, tall, blond, traditionally attractive, and she's pretty damned into me (like --calling me at 11pm last night to ask if I wanted her to come cheer me on at my 5k this weekend-- into me). We actually have a lot in common, down to what we want out of a relationship. She's mature, honest, and communicates extremely well. But....well honestly, just that there's a but in there somewhere should tell me something. So, does it just go back to that basic instinctual feeling of chemistry, passion, lust, desire, attraction, (...yada, yada, yada), that's akin to love at first sight? Or, can something develop over time that's real and lasting? Shit if I know. My problem is, do I want to stick around to find out? Should I heed the adage, nothing ventured, nothing gained, or have I ventured enough? Two dates, multiple email and phone conversations, and the most I can say about her afterward is, it was great conversation. Maybe I should take a cue from my failed marriage...after all, that was essentially a six year great conversation...and move on before any more time is invested or attachment is formed?

Woof....I need a liquor drink.