bigO: I am somewhat of a political nerd and former law enforcement, so both definitely affect my opinions.
1) The proceedings to date have been dictated by the majority (Democrats) without trying to garner any input from the minority (Republicans). In the past, the majority has always reached out to the minority, regardless if the minority agreed or not (ex: Pres Clinton's impeachment) for both the appearance of bipartisanship in the House and publicly. The proceedings to date have not even come close to mirroring precedent.
2) Speaking from a legal point of view, I do not know any prosecutor who would accept a case such as this to send to the Grand Jury. Nothing in the report from Rep Schiff has anything which would be codified in the federal legal system, nor would be recognized by common law. Again, this breaks with precedent.
3) Along with #2, all of the "damaging" testimony to date has been hearsay and supposition (opinion). Yes, there is the actual call, but no specific demands tying things together. Couple with the facts the Ukrainians did not know the aid was being withheld, nor did their President feel pressured, would seem to undercut the argument.
4) I was interested in the constitutional witnesses (again - political nerd / law enforcement), but I was struck the first witness was called by Republicans while the remaining three were called by Democrats. Traditionally, it would be 2-2 in the spirit of bipartisanship. However, I was struck by the one witness who seemed to really push back on impeachment.
5) At least to me the whole process seems to be really rushed. If the Democrats are going to truly investigate Pres Trump, then put the time and effort in to do it correctly. Looking at the history of when the House issues subpoenas (ex: Pres Clinton / AG Holder / Pres Nixon), the House traditionally takes its time to work through various issues and looks to resolve them without legal action. We have even seen that be the case fairly recently (AG Barr releasing additional information regarding the Mueller report). But, the rush to issue subpoenas, and the apparent unwillingness for the courts to work through various key witnesses (ex: Bolton / Mulvaney) seems more of a drive to have Articles of Impeachment voted upon versus getting the whole story.
6) I am also fairly troubled with the report from Rep Schiff as not only does it throw a bunch of stuff against the wall which has not been fully investigated, but it released a great deal of phone numbers / conversations to the public. This should be immediately addressed in the strongest of terms as any prosecutor who did this would not only be subjected to firing, but potential jail time as well.
7) Initially I expected the House to vote on 3-4 Articles of Impeachment. But, as Rep Nadler accepted the report from Rep Schiff on the whole, and Rep Pelosi ordered Rep Nadler to move forward with Articles, I think the number could grow exponentially. This might be an attempt to see what sticks or at least give some Reps cover so they could vote against some in districts where Pres Trump did very well.
8a) The whole scenario changes once it hits the Senate. I have seen more than a few promote the idea the Senate will call various people to the trial (Pompeo / Bolton / Mulvaney), but I doubt that will happen. Although the Chief Justice presides, it is really the majority in the Senate which dictate what will or will not take place. It has been reported Sen Schumer has rebuffed negotiations with Sen McConnel regarding the rules of a proposed trial. If that continues, then Sen McConnel, with the Republican majority, could have a simple vote on the rules regardless of what the minority want (i.e. what the House did).
8b) Unless something changes, my presumption is the trial will last 4-8 weeks with possibly 1-Republican voting for removal while potentially 2-Democrats will vote against.
Of course, all of the above could change if first-hand information is revealed which directly contradicts what Pres Trump has said to date. But, as independents have been moving away from impeachment, and the process has been very one-sided, if nothing changes I expect Pres Trump to stay in office.