1) No
2) I did send a updated transcripts. I only think it was required at 1 or 2 schools, but if you have strong grades and/or had a heavy set of couses that semester, it may help. Fall senior year was my most impressive semester on paper, so I definitely wanted to make it part of my application. OTOH, if you slacked off or struggled because of the attention needed for the GRE, then perhaps by submitting the apps before your semester ends, you can justify not including fall grades.
3) No problems at all! I'd advise everyone to take it in October. (If you can be prepared in April, then sure, do it then, but most of us won't be... don't rush it prematurely unless you're sure you'll get a 990.) October has so many advantages:
- Know your score BEFORE applying (duh, this may help

)
- If something goes wrong, cancel your scores and retake it in November.
- You can most of your studying in the second half of the summer and it will still be fresh in your mind in October... and you can probably afford to blow off your classes for studying until October, but not November!
4) About REUs, it's natural to worry whether your success with REU applications is a precursor to your success with grad school apps, but it absolutely isn't! Every time someone brings this up, I share the following because I don't want people to get demoralized. Most of the good students here and elsewhere have had horrible sucecss rates with REUs, but did quite well with GS apps. I always laugh at the fact that I was rejected by REU programs at Wright State University (never heard of them until I applied), University of Nevada at Last Vegas ($$$haha$$$) and Lehigh (who?), but was later accepted to grad programs at Caltech, Stanford and Princeton....
Here are the basic reasons why REUs are so much harder...
---There are typically only 8-10 REU spots available, which is usually less than the size of the entering graduate class at the schools that host these programs. And there are far fewer REU sites than physics grad programs. This is offset a bit by the fact that internationals can't apply to REUs, but there are still fewer spots per domestic applicant in REUs than in G.S.
----NSF emphasizes diversity, so over half the spots at a typical REU (
Ex. 1, Ex. 2, Ex. 3) are allotted to women and underrepresented minorities. Thus, most applicants (white males) are at a disadvantage. (Graduate programs also like diversity, but I doubt the student at my REU program who had a 2.7 GPA is at grad school right now.

)
---At the time students apply to REUs, middle soph or junior year, there is an infinite supply of ~4.0 students with research experience and there is no way to distinguish between them since we haven't taken the GRE or many advanced courses yet. By senior year, grad programs have much more info to distinguish among the "good" students.
---Connections sometimes play a big part in REU admissions, whether it's the student having prior communication with a prof at the program, or the prof knowing his recommender.
---The goal of some programs is give research opportunities to students who haven't had them before. Others want to bring in students who they can extract the most benefit out of in the lab. Thus, they're either bringing in the overachievers who've been doing research since high school and already have publications before junior year, or they're focusing on students from places like liberal arts schools that don't have research.
Thus overall, the typical white male student with good grades and just decent research experience is facing ridiculous odds and should apply to as many programs as possible to maximize their chance of getting in somewhere. I applied to I think 9 and was accepted to 2 and rejected by 8... (U of Oklahoma sent me both an acceptance e-mail and a rejection letter). However, I was a soph the year I applied and a few of the rejection letters insinuated they give preference to juniors, so maybe I would've done better the next year.
Edit: Damn, I completely messed up earlier, I wrote "accepted to 8 and rejected by 2, lol